Since the past, an optical module has been used in optical communication using optical fibers, the optical module including a light-emitting element such as a surface light-emitting laser. For example, a vertical cavity surface emitting laser (VCSEL).
In this type of optical module, an optical module component referred to as an optical receptacle is used. The optical receptacle is used in optical transmission via optical fiber by light that includes communication information and has been emitted from the light-emitting element being coupled with an end face of the optical fiber.
In addition, since the past, various proposals have been made regarding the optical module to monitor the light (intensity and amount of light) emitted from the light-emitting element, for the purpose of stabilizing output characteristics of the light-emitting element against temperature changes and adjusting optical output.
For example, Patent Literature 1 and Patent Literature 2 propose the use of a photoelectric conversion device in which a light-receiving element for monitoring is enclosed together with a light-emitting element in a package referred to as a TO-CAN. Some of the outgoing light from the light-emitting element is reflected to the light-receiving element side as monitor light at a glass window of the package.
However, in a CAN-package type photoelectric conversion device such as this, during high-frequency drive, crosstalk occurs in some instances as a result of electromagnetic waves leaking from a section of wiring connected to the light-emitting element. In such instances, support of high-speed communication of 10 Gbps or more becomes difficult. Furthermore, in the module using the CAN package, the maximum diameter of the optical receptacle is 6 to 7 mm in, for example, a CAN referred to as TO-46. Therefore, size reduction is difficult.
On the other hand, in a substrate-mounted photoelectric conversion device in which the light-emitting element is mounted on a circuit board, unlike the CAN-package type, there are no issues regarding crosstalk. In addition, there are advantages, such as reduced number of components, reduced cost, and reduced size. However, because a glass window is not provided, it is difficult to include a function for generating monitor light on the photoelectric conversion device side.
Therefore, for example, as shown in Patent Literature 3, proposals have been made to actualize stable high-speed communication accompanying monitoring by a reflective surface for reflecting some of the outgoing light from the light-emitting element towards the light-receiving element side as monitor light being formed on the optical receptacle side to support the substrate-mounted photoelectric conversion device.